1. Field of the Invention
This invention relates to a branched alpha-olefin polymer composition having excellent melt-flowability, good moldability and excellent melt tension, and to a process for its production.
More specifically, it relates to a branched alpha-olefin polymer composition having excellent meltflowability, good moldability and excellent melt tension and comprising at least two branched alpha-olefin polymers composed of (A) recurring units derived from a branched alpha-olefin containing 5 to 10 carbon atoms and having a branch at the 3-position or a position of a higher number and (B) recurring units derived from a linear alpha-olefin containing 2 to 20 carbon atoms, and to a process for producing said polymer composition by a multiplicity of polymerization steps.
2. Description of the Prior Art
There have been a number of attempts to produce branched alpha-olefinic polymers having excellent transparency and thermal stability by polymerizing or copolymerizing branched alpha-olefins such as 4-methyl-1-pentene and 3-methyl-1-pentene in the presence of stereo-regular Ziegler catalysts comprising titanium trihalides such as TiCl.sub.3. The resulting branched alpha-olefinic polymers have a broad molecular weight distribution and execllent melt flowability and moldability, but have the defect of poor stereoregularity and, rigidity. Furthermore, the catalysts have poor polymerization activity.
The present applicant studied the production of branched alpha-olefinic polymers using conventional titanium trihalide catalysts, and found that alpha-olefinic polymers having excellent stereoregularity and rigidity can be obtained by employing a method which comprises polymerizing branched alpha-olefins in the presence of a catalyst formed from a highly active titanium catalyst component, an organoaluminum compound and an organosilicon compound. This finding was proposed in Japanese Laid-Open Patent Publication No. 206418/1984. The branched alpha-olefinic polymers obtained by the method described in this patent document have excellent stereoregularity and rigidity, but are still desired to be improved in such properties as melt flowability, moldability and melt tension.